Well, I am no expert, and my hen may be different from others but here is what I know.

My Lacy had her chicks with her for 4 weeks. At that time, she started pecking at them and actually chasing them away from her. However, she still has them under her wings at night warming them at 5 weeks.

In the daytime, when they are free ranging you wouldn't know who is their mom but you do at night.